Propeller Fan Blade Warping Angle Distribution for Noise Reduction
Solution Overview
Problem
Existing propeller fan designs with warping blades fail to sufficiently suppress radial-direction flows, leading to unstable blade tip vortices and increased noise due to collisions between radial-direction flows and blade tip vortices.
Innovation Solution
A propeller fan design with a specific warping angle distribution, where the relationship (θ2−θ1)/(r2−r1)>(θt−θ3)/(rt−r3)≥0 is satisfied, with distinct parts of the blade having varying distances from the rotation axis and warping angles, stabilizing the blade tip vortex and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the warping angle gradually increases from the base toward the tip end of the moving blade, then the blade can generate sufficient centrifugal force, but the radial-direction flow on the suction surface collides with the blade tip vortex, causing noise increase
Solution Approach 1:
The patent applies local quality by dividing the blade into multiple sections (first, second, third, and tip parts) with different warping angle characteristics. The first part has a larger warping angle to generate centrifugal force, while the second part has a smaller warping angle to suppress radial-direction flow and prevent collision with the blade tip vortex, thereby reducing noise. This localized differentiation of warping angles resolves the contradiction between power generation and noise reduction.
2Object-generated harmful factors
If the warping angle is increased to suppress radial-direction flow, then noise may be reduced, but the blade tip vortex formation becomes unstable
Solution Approach 1:
The patent employs parameter changes by precisely controlling the warping angle distribution along the blade span. The relationship (θ2−θ1)/(r2−r1)≥(θt−θ3)/(rt−r3)≥0 defines specific parameter ranges for different blade sections. This parameter optimization allows sufficient suppression of radial-direction flow to reduce noise while maintaining stable blade tip vortex formation through appropriate warping angle selection in the second part of the blade.
3Device complexity
If a uniform warping angle distribution is used, then the blade structure is simple, but the radial-direction flow cannot be sufficiently suppressed, leading to noise increase
Solution Approach 1:
The patent implements local quality by creating non-uniform warping angle distribution across different blade sections. The first part has a larger warping angle while the second part has a smaller warping angle, specifically designed to suppress radial-direction flow and reduce noise. This localized differentiation maintains relative structural simplicity while achieving the noise reduction goal.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed design effectively suppresses radial-direction flows and leak flows, stabilizing the blade tip vortex, thereby reducing noise and improving the efficiency of the propeller fan.
Implementation Method 1
a radial-direction flow, which is an air flow on the suction surface of the moving blade flowing in the radial direction due to a centrifugal force
Implementation Method 2
a blade tip vortex formed on the suction surface at a tip end part of the blade
Data Source
AI summary
A propeller fan includes a shaft part and a blade. The blade includes a basal part connected to the shaft part, a first part positioned either at the basal part or closer to an outer circumference of the propeller fan than is the basal part and away from the rotation axis by a distance r1, a second part positioned away from the rotation axis by a distance r2 that is longer than r1, a third part positioned away from the rotation axis by a distance r3 that is longer than or equal to r2, and a tip part positioned at an outer circumferential end of the blade and away from the rotation axis by a distance rt that is longer than r3. A relationship expressed as (θ2−θ1)/(r2−r1)>(θt−θ3)/(rt−r3)≥0 is satisfied.